There is a problem that if a fingerprint (the fingerprint refers to a pattern made by lines of raised opening portions of perspiratory glands (ridge lines) present in the skin of finger tips, and to a trace of deposition of the pattern on a surface of an object) is deposited by a human finger touching a surface of an object, the fingerprint is recognized and the appearance gives an unpleasant impression of being seemingly dirty. An example of this is an incident where when the casing of a cellular phone is grabbed, fingerprints are deposited, the fingerprints are conspicuous, impairing the impression of cleanliness. Particularly recently, electronic appliances operated by fingers are increasing in number, for example, smart phones and touch panels, keyboards, remote controllers of televisions and air-conditioners and the like.
Furthermore, there is a problem that if a fingerprint deposits on an image display portion of an image display appliance, a signal display portion such as a warning light or the like, a surface of a lens, a mirror or the like, the visibility deteriorates due to unclear appearance of a displayed image, a displayed signal or a reflected image, difference in reflection rate between a site where a fingerprint is deposited and a site where a finger print is not deposited and the like. Examples are the liquid crystal screens of smart phones, televisions, car navigations and personal computers, signal display lights for guiding, warning and escape guidance, the lenses of glasses, sunglasses, telescopes and cameras, the transparent covers of the dials of clocks and watches, the rearview mirrors and inner rearview mirrors of vehicles and the like. Once a fingerprint deposits on these appliances, the fingerprint degrades the visibility of an object.
Furthermore, in recent years, various kinds of displays of smart phones, televisions, personal computer monitors or the like employ an antireflection member (antireflection film) whose surface has gloss to make images look high in contrast. However, such a material having glossiness makes it easy for a fingerprint to be visually recognized, which is an issue.
For such a problem, Japanese Patent Application Publication No. 2009-122416 proposes as a member that makes it hard for a fingerprint to be visually recognized (hereinafter, the property that a fingerprint on an article's surface is hard to be conspicuous, hard to be visually recognized, or hard to be seen will be termed the anti-fingerprint property) an “optical thin membrane film in which on one of surfaces of a substrate material there is formed a thin membrane layer that at least includes a low-refractive layer whose refractive index at a light wavelength of 550 nm is less than 1.75 or a high-refractive layer whose refractive index at the light wavelength of 550 nm is greater than or equal to 1.75, or both the layers, the optical thin membrane film being characterized in that when an oleic acid whose dry membrane thickness is 20 μm is applied onto a surface of the thin membrane layer, a CIELAB (conforming to JIS Z8729) color difference ΔE*ab (={(ΔL*)2+(Δa*)2+(Δb*)2}1/2) with a D65 light source, a 5° incidence, a 2° view, and regular reflected light between the optical thin membrane film to which the oleic acid has been applied and the optical thin membrane film to which the oleic acid has not been applied is less than or equal to 5.”
Furthermore, as a method of making it hard for a finger print to be visually recognized, Japanese Patent Application Publication No. 10-310455 proposes an “article made of a glass substrate which is characterized in that at least a portion of a surface of the glass substrate has a silica foundation layer and b a water-repellent and oil-repellent coating characterized by having been treated with perfluoroalkyl alkylsilane,” and Japanese Patent Application Publication No. 2010-100804 proposes an “active energy ray hardening composition containing: an active energy ray hardening compound (A) having a fatty acid ester structure made up of a fatty acid whose carbon number is greater than or equal to 6, a polyalkylene oxide chain and a acryloyl group or a methacryloyl group; and an active energy ray hardening compound (B) different from the active energy ray hardening compound (A).”
Still further, as a technology that focuses on the configuration of a surface to make it harder for a fingerprint to be visually recognized, Japanese Patent Application Publication No. 2004-5005 proposes a “substrate plate for a touch panel in which a surface configuration of the rough-surfaced layer is 100 to 300 nm in center line average roughness (Ra), and is greater than or equal to 50 μm in average interval between bumps and dips,” and Japanese Patent Application Publication No. 2010-259971 proposes a “composite in which a substrate plate is provided, and an anti-fingerprint deposition coating cover that contains a silicon compound and a hydrophilic metal oxide fine particle whose average particle diameter is 1 to 100 nm is formed on a surface of the substrate plate, the substrate plate being characterized in that glossiness of the coating cover is less than or equal to 8 and the color difference of the coating cover is less than 4.6.”
The fingerprint is what is formed on an object such as a surface of a forming material as a liquid deposited on a human finger is transferred to a surface of the object such as the surface of the forming material when the human finger touches the object. The liquid that constitutes the fingerprint is in the state of a so-called dispersion in which water, organic salts (uric acid salts or the like), sebum (oleic acid, triolein or the like), and also dust present in the human living environment and particles contained in cosmetics (titanium oxide, zinc oxide, silica or the like) are mixed.
On the other hand, JP '416 discloses that, as a mock material for a fingerprint, oleic acid is applied to a surface of an optical thin membrane film, and a color difference calculated from the regular reflected light spectra of simple incident light from the paint-applied portion and a non-paint-applied portion is made less than or equal to specific value.
Therefore, in JP '416, in terms of the fingerprint deposition characteristic, since the fluidity of the liquid that constitutes a fingerprint greatly differs depending on the presence of particles, the mocking of the amount of deposition and the configuration of deposition is insufficient. Furthermore, in terms of evaluation of the color difference between the paint-applied portions/non-paint-applied portions, the effect of light scattering due to the presence of particles cannot be evaluated, and furthermore, the simple incident light is evaluated only from the regular reflected light. Therefore, a state in which a human actually perceives visual sensation cannot be reproduced. In consequence, it can be considered that in JP '416, the effect of making a fingerprint less conspicuous is insufficient.
There is thus a need to provide a forming material that has an anti-fingerprint property while maintaining glossiness or transparency and a scratch resistance that is needed for practical use, a paint composition capable of forming a layer that has an anti-fingerprint property, and a production method for the aforementioned layer. In connection with the foregoing task, the known technologies are in the following situation.
First, with regard to the visibility of a fingerprint, JP '416 proposes an optical thin membrane film that causes the color difference between before and after oleic acid is applied to be less than or equal to a certain value. However, according to our checking the visibility of a fingerprint under various conditions, it has been found that, with the property according to JP '416 alone, the effect of causing a fingerprint to be less conspicuous is insufficient.
Furthermore, the method of JP '455 provides a substrate surface with an undercoat layer, and a water-repellent and oil-repellent cover is provided on the layer, and the method of JP '804 causes the boundary line of a fingerprint with a surrounding hardening paint membrane to be less conspicuous by approximating the refractive index of the hardening paint membrane to the refractive index of components of the fingerprint and making the height of the deposited fingerprint as low as possible. However, according to our checking the visibility of a fingerprint under various conditions, the former shows considerable decline in glossiness, and the latter is insufficient in the foregoing effect with fingerprints rich in sebum, that is, neither of them can solve the task.
Still further, JP '005 and JP '971, while certainly being able to reducing the visibility of fingerprints, cannot provide a demanded glossiness, and, with the configuration of the surface being a rough surface, have not reached an idea regarding our technique.